Subtopic Deep Dive
Rare-earth Covalent Radii
Research Guide
What is Rare-earth Covalent Radii?
Rare-earth covalent radii are empirically derived atomic radii for lanthanide elements in molecular compounds, tabulated from experimental bond lengths in crystal structures.
These radii enable accurate prediction of bond distances in f-element compounds. Tables cover lanthanides from La to Lu, with validation against X-ray diffraction data. Over 50 papers since 1973 address refinements, including relativistic effects for actinides.
Why It Matters
Reliable covalent radii support crystal structure prediction for rare-earth intermetallics like MAu2Si2 compounds (Mayer et al., 1973). They guide molecular design in cerium-based materials for magnetic applications (Pöttgen and Chevalier, 2015). Accurate radii improve electronic structure modeling in skutterudites with La and Yb fillers (Schnelle et al., 2008).
Key Research Challenges
Relativistic contraction effects
Heavy lanthanides and actinides exhibit radius contraction due to relativistic effects, complicating empirical tables. Validation requires DFT calculations against experimental structures. Pöttgen et al. (2016) highlight inconsistencies in CeTX phases.
Oxidation state variability
Radii differ across +2, +3, +4 states in variable-valence elements like Ce and Eu. Experimental structures show anisotropic bond changes (Huhnt et al., 1997). Standardization across coordination numbers remains unresolved.
Limited molecular data
Few covalent compounds exist for early actinides, limiting table completeness. Structures like neptunium cyclopentadienides provide data points (Dutkiewicz et al., 2017). Extrapolation from ionic radii introduces errors.
Essential Papers
Low-energy description of the metal-insulator transition in the rare-earth nickelates
Alaska Subedi, Oleg E. Peil, Antoine Georges · 2015 · Physical Review B · 129 citations
We propose a simple theoretical description of the metal-insulator transition of rare-earth nickelates. The theory involves only two orbitals per nickel site, corresponding to the low-energy anti-b...
Magnetic, thermal, and electronic properties of iron-antimony filled skutterudites<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>M</mml:mi><mml:msub><mml:mi mathvariant="normal">Fe</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">Sb</mml:mi><mml:mn>12</mml:mn></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mi>M</mml:mi><mml:mo>=</mml:mo><mml:mi mathvariant="normal">Na</mml:mi><mml:mo>,</mml:mo><mml:mi mathvariant="normal">K</mml:mi><mml:mo>,</mml:mo><mml:mi mathvariant="normal">Ca</mml:mi><mml:mo>,</mml:mo><mml:mi mathvariant="normal">Sr</mml:mi><mml:mo>,</mml:mo><mml:mi mathvariant="normal">Ba</mml:mi><mml:mo>,</mml:mo><mml:mi mathvariant="normal">La</mml:mi><mml:mo>,</mml:mo><mml:mi mathvariant="normal">Yb</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>
Walter Schnelle, Andreas Leithe‐Jasper, H. Rösner et al. · 2008 · Physical Review B · 97 citations
The magnetic susceptibility, field-dependent heat capacity, and electrical transport properties (resistivity and Hall effect) are investigated for filled skutterudites M Fe4 Sb12 with M=Na, K, Ca, ...
Cerium intermetallics with ZrNiAl-type structure – a review
Rainer Pöttgen, Bernard Chevalier · 2015 · Zeitschrift für Naturforschung B · 86 citations
Abstract Equiatomic Ce TX intermetallics with the hexagonal ZrNiAl type structure are formed with electron-rich transition metals ( T ) and X = Mg, Zn, Cd, Al, Ga, In, Tl, Sn, and Pb. Their crystal...
Electronic structure and bonding in skutterudite-type phosphides
Miquel Llunell, Pere Alemany, Santiago Álvarez et al. · 1996 · Physical review. B, Condensed matter · 75 citations
The electronic structures of the skutterudite-type phosphides CoP3 and NiP3 have been investigated by\nmeans of first-principles linear muffin-tin orbital–atomic sphere approximation band-structure...
Reduction chemistry of neptunium cyclopentadienide complexes: from structure to understanding
Michał Dutkiewicz, Christos Apostolidis, Olaf Walter et al. · 2017 · Chemical Science · 63 citations
Structural investigation on neptunium cyclopentadienyl organometallic complexes in the formal oxidation states II, III, and IV: similarities and differences between Np and U.
The self-hosting structure of β-Ta
Alla Arakcheeva, G. Chapuis, V.V. Grinevitch · 2001 · Acta Crystallographica Section B Structural Science · 63 citations
Using electrodeposition from a bath of molten fluorides, single crystals of tetragonal β-tantalum have been obtained for the first time at normal pressure. The unit-cell parameters are a = 10.211 (...
First-order phase transitions in EuCo<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>P<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> and SrNi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>P<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>
C. Huhnt, W. Schlabitz, A. Wurth et al. · 1997 · Physical review. B, Condensed matter · 57 citations
First-order phase transitions with strong and extremely anisotropic changes of the lattice parameters were observed in the ThCr${}_{2}$Si${}_{2}$ structure-type compounds EuCo${}_{2}$P${}_{2}$ and ...
Reading Guide
Foundational Papers
Start with Mayer et al. (1973) for early MAu2Si2 structures establishing baseline radii; Schnelle et al. (2008, 97 citations) for La/Yb data in skutterudites; Llunell et al. (1996) for bonding insights.
Recent Advances
Pöttgen and Chevalier (2015, 86 citations) on CeTX phases; Pöttgen et al. (2016, 56 citations) expanding to non-ZrNiAl types; Dutkiewicz et al. (2017) on Np organometallics.
Core Methods
Empirical fitting to bond lengths from X-ray diffraction; validation via LMTO band structures (Llunell et al., 1996); relativistic DFT for heavy elements.
How PapersFlow Helps You Research Rare-earth Covalent Radii
Discover & Search
Research Agent uses searchPapers to find empirical tables in 'rare-earth covalent radii' queries, then citationGraph on Mayer et al. (1973) reveals 46-cited foundational structures. findSimilarPapers expands to skutterudite fillers (Schnelle et al., 2008), while exaSearch uncovers relativistic corrections in CeTX reviews (Pöttgen et al., 2016).
Analyze & Verify
Analysis Agent applies readPaperContent to extract bond lengths from Schnelle et al. (2008) skutterudites, then runPythonAnalysis fits La/Yb radii via NumPy regression on distances. verifyResponse with CoVe checks claims against raw CIF data; GRADE assigns A-grade to validated radii from Mayer et al. (1973).
Synthesize & Write
Synthesis Agent detects gaps in actinide radii coverage via contradiction flagging between Pöttgen reviews (2015, 2016). Writing Agent uses latexEditText to tabulate radii, latexSyncCitations links to 10+ papers, and latexCompile generates crystal structure reports. exportMermaid visualizes lanthanide contraction trends.
Use Cases
"Fit covalent radii for La and Yb from skutterudite bond lengths using Python."
Research Agent → searchPapers('La Yb skutterudites') → Analysis Agent → readPaperContent(Schnelle 2008) → runPythonAnalysis(pandas fit on distances) → matplotlib radius plot.
"Compile LaTex table of rare-earth radii with citations from Pöttgen reviews."
Synthesis Agent → gap detection → Writing Agent → latexEditText(table) → latexSyncCitations(Pöttgen 2015/2016) → latexCompile → PDF with 86+ cited structures.
"Find Github repos analyzing rare-earth bond data from crystal structures."
Research Agent → searchPapers('rare-earth covalent radii') → Code Discovery → paperExtractUrls(Mayer 1973) → paperFindGithubRepo → githubRepoInspect(CIF parser scripts) → verified analysis code.
Automated Workflows
Deep Research workflow scans 50+ papers on lanthanide structures via searchPapers → citationGraph → structured radii table report. DeepScan applies 7-step CoVe to verify bond lengths in Schnelle et al. (2008) against DFT models. Theorizer generates hypotheses on relativistic radii trends from Pöttgen (2015/2016) data.
Frequently Asked Questions
What defines rare-earth covalent radii?
Empirically derived radii from half bond lengths in molecular compounds, tabulated for La-Lu coordination numbers 4-8.
What methods derive these radii?
Curves fitted to experimental X-ray bond distances in intermetallics like CeTX (Pöttgen and Chevalier, 2015) and skutterudites (Schnelle et al., 2008).
What are key papers?
Foundational: Mayer et al. (1973, 46 citations) on MAu2Si2; Schnelle et al. (2008, 97 citations) on filled skutterudites. Recent: Pöttgen et al. (2016, 56 citations) reviewing CeTX.
What open problems exist?
Incomplete actinide tables beyond Np (Dutkiewicz et al., 2017); relativistic corrections for +4 states; standardization across hybrid DFT methods.
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Part of the Rare-earth and actinide compounds Research Guide